2.2 Introduction to Salts

• Meaning and classification of salts
• Solubility of salts in water
• Methods of preparing salts
• Behaviour of salts exposed to air: efflorescence, deliquescence, hygroscopy
• Applications of salts in day-to-day life

• classify different salts based on their properties
• prepare salts using appropriate methods in the laboratory
• describe the behaviour of salts when exposed to air
• outline applications of salts in day-to-day life
• appreciate applications of salts in day-to-day life

“Why does salt in a shaker clog in humid weather?”

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1. Salts and solubility
   40 min · 2 practice tasks · quiz
   What a salt is, which dissolve, and why that decides how you make them.
2. Preparing salts and their behaviour in air
   40 min · 2 practice tasks · quiz
   Choosing a method from solubility, and why some salts clog and others crumble.
3. A salt is an ionic product
   40 min · 1 practice tasks · quiz
   A salt is the ionic compound left when acid hydrogen is replaced by a metal or ammonium ion.
4. Naming salts from the parent acid
   40 min · 1 practice tasks · quiz
   The acid gives the second half of the salt name; the metal or ammonium gives the first.
5. Normal salts
   40 min · 1 practice tasks · quiz
   A normal salt has every replaceable hydrogen of the acid swapped for a metal or ammonium.
6. Acid salts
   40 min · 1 practice tasks · quiz
   An acid salt still contains replaceable hydrogen because only some of the acid hydrogen was swapped.
7. Basic salts
   40 min · 1 practice tasks · quiz
   A basic salt still contains hydroxide (or oxide) because the base was not fully neutralised.
8. Double salts
   40 min · 1 practice tasks · quiz
   A double salt crystallises with two different cations (or two salts) in a definite ratio, such as potash alum.
9. Hydrated and anhydrous salts
   40 min · 1 practice tasks · quiz
   Hydrated salts contain water of crystallisation in a fixed amount; anhydrous salts do not.
10. Water of crystallisation
    40 min · 1 practice tasks · quiz
    Water of crystallisation is water chemically combined in a definite ratio in a crystal; heating can drive it off.
11. Salts that always dissolve
    40 min · 1 practice tasks · quiz
    All sodium, potassium and ammonium salts, and all nitrates, are soluble in water.
12. Chloride and sulphate exceptions
    40 min · 1 practice tasks · quiz
    Most chlorides and sulphates dissolve; silver and lead chlorides, and barium, lead and calcium sulphates, do not.
13. Most carbonates and hydroxides do not dissolve
    40 min · 1 practice tasks · quiz
    Carbonates and hydroxides are insoluble except those of sodium, potassium and ammonium; calcium hydroxide is slightly soluble.
14. Choosing how to make a salt
    40 min · 1 practice tasks · quiz
    Solubility decides the method family: precipitation for insolubles, acid plus a reagent then crystallisation for solubles.
15. Preparing a salt from acid and alkali
    40 min · 1 practice tasks · quiz
    When both reagents dissolve, use titration to hit the end point, then evaporate and crystallise without indicator.
16. Preparing a salt from acid and an insoluble base
    40 min · 1 practice tasks · quiz
    Add excess insoluble oxide or hydroxide to warm dilute acid, filter, then crystallise the soluble salt.
17. Preparing a salt from acid and a carbonate
    40 min · 1 practice tasks · quiz
    Acid plus a carbonate gives a salt, water and carbon dioxide; use excess insoluble carbonate, then filter and crystallise.
18. Preparing a salt from acid and a metal
    40 min · 1 practice tasks · quiz
    A metal above hydrogen reacts with dilute acid to give a soluble salt and hydrogen; use excess metal, then filter and crystallise.
19. When the metal will not make the salt
    40 min · 1 practice tasks · quiz
    Copper, silver and gold do not displace hydrogen from dilute acids; sodium and potassium are too violent. Choose oxide, carbonate or alkali instead.
20. Precipitation of insoluble salts
    40 min · 1 practice tasks · quiz
    Mix two solutions that supply the needed ions; the insoluble salt falls out and is filtered, washed and dried.
21. Ionic equations for precipitation
    40 min · 1 practice tasks · quiz
    Write only the ions that form the solid. Spectator ions stay in solution and are omitted.
22. Filtering, washing and drying a precipitate
    40 min · 1 practice tasks · quiz
    Collect the solid on filter paper, wash soluble impurities away with distilled water, then dry without decomposing it.
23. Crystallising a soluble salt
    40 min · 1 practice tasks · quiz
    Concentrate the solution, then cool slowly so large pure crystals grow. Boiling dry gives a powder and can destroy hydrates.
24. Efflorescence
    40 min · 1 practice tasks · quiz
    An efflorescent salt loses water of crystallisation to dry air and crumbles from crystals to powder.
25. Deliquescence and hygroscopy
    40 min · 1 practice tasks · quiz
    Deliquescent salts absorb water and dissolve in it. Hygroscopic substances absorb water but stay solid. That is why a shaker clogs.
26. Magadi soda as a salt
    40 min · 1 practice tasks · quiz
    Lake Magadi in Kajiado yields trona processed to sodium carbonate, a soluble carbonate salt used in glass, soap and cooking.
27. Kenyan table salt
    40 min · 1 practice tasks · quiz
    Coastal solar pans such as Gongoni evaporate seawater to NaCl. The food product is iodised to prevent goitre.
28. Salts in food, farm, clinic and industry
    40 min · 1 practice tasks · quiz
    The same class of ionic compounds seasons food, feeds crops, sets plaster, treats disease and runs Kenyan industry.
29. Safety when preparing salts
    40 min · 1 practice tasks · quiz
    Goggles, correct heating, no tasting, and extra care with barium, lead, silver nitrate and acids make salt practicals legitimate science.
30. Putting salts together
    40 min · 1 practice tasks · quiz
    Classify a salt, read solubility, choose a preparation method, and name Kenyan examples from Magadi to Gongoni.